Xinyuan Zhou

Air pollution is pushing wind speed into a regulator of surface solar irradiance in China

Analysis in 27 cities across China shows that surface solar irradiance (SSI) and wind speed track similar decadal trends in 1961–2011, suggesting wind speed as a possible regulator of SSI. This assumption is further confirmed by the continuously widening gap in annually averaged daily SSI between windy and windless clear-sky days with worsening air pollution. Wider gaps are noted for more polluted cities and seasons. The gap in SSI between windy and windless conditions could therefore serve as a good indicator for air quality. The regulatory effect of wind speed on SSI starts to be important when air pollution index exceeds the boundary of 125. A plausible mechanism of wind speed regulating SSI through interactions with aerosols is proposed. There are two cut-off points of 2.5 m s−1 and 3.5 m s−1 wind speeds. Winds <2.5 m s−1 noticeably disperse air pollutants and thereby enhance SSI. Above the 2.5 m s−1 threshold, air pollution and SSI become largely insensitive to changing wind speeds. Winds in excess of 3.5 m s−1 could enhance aerosol concentration probably by inducing dust-storms, which in turn attenuate SSI.

Effects of dynamic feeding low and high methionine diets on egg quality traits in laying hens

&NA; This study was conducted to investigate effects of dynamic feeding low and high methionine (MET) diets on performance, egg quality traits, and serum metabolites in laying hens. A total of 180 laying hens (Brown Hy‐line, 41 wk old) were allocated into 3 equal groups with 6 replicates each. The average egg production (EP) of each group was around 87% during one‐week statistics before the formal experiment (P = 0.989). The control group (CON) received the control diet (contained 0.30% MET) at both 07:30 h and 15:30 hours. The low‐high group (LH) received a low MET diet (containing 0.27% MET) at 07:30 h and high MET diet (containing 0.33% MET) at 15:30 hours. The high‐low group (HL) received a high MET diet at 07:30 h and low MET diet at 15:30 hours. After 10 wk, blood samples were collected at 4‐hour intervals in a daily cycle initially starting at 07:30 h before feeding. Results showed that the MET intake of a d was not influenced by the treatments (P > 0.05), respectively. The EP of the LH and HL group increased by 2.28 and 2.45% when compared with the CON group (P > 0.05). The hens in the LH group had a lower albumen ratio and thicker eggshell thickness than both CON and HL groups. Egg yolk ratio of the LH group was higher than the HL group (P < 0.05). The serum total cholesterol (TC), total triglyceride (TG), total protein (TP), and calcium (Ca) of the LH group was significantly lower at 07:30 h than the CON and HL groups, and the serum TG of the HL group was lower at 07:30 h than the CON group (P < 0.05). Meanwhile, the LH group also had the lowest value of serum TP at 23:30 h and 03:30 h (P < 0.05). These results demonstrated that dynamic feeding low and high MET diets might alter the circadian variation of serum TC, TG, TP, and Ca, which is consistent with the change of component ratio of egg albumen and yolk and eggshell thickness.

Ag-Modified In2O3 Nanoparticles for Highly Sensitive and Selective Ethanol Alarming

Pure In2O3 nanoparticles are prepared by a facile precipitation method and are further modified by Ag. The synthesized samples are characterized by scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, Raman and UV-Vis spectra. The results show the successful heterojunction formation between Ag and In2O3. Gas sensing property measurements show that the 5 mol % Ag-modified In2O3 sensor has the response of 67 to 50 ppm ethanol, and fast response and recovery time of 22.3 and 11.7 s. The response is over one magnitude higher than that of pure In2O3, which can be attributed to the enhanced catalytic activity of Ag-modified In2O3 as compared with the pure one. The mechanism of the gas sensor can be explained by the spillover effect of Ag, which enhances the oxygen adsorption onto the surface of In2O3 and thus give rise to the higher activity and larger surface barrier height.

MOF-derived hierarchical ZnO/ZnFe2O4 hollow cubes for enhanced acetone gas-sensing performance

ZnO/ZnFe2O4 hollow cube composites with heterogeneous structure are synthesized by a facile strategy through simple and direct pyrolysis of FeIII-modified Zn-based metal–organic frameworks. The as-synthesized ZnO/ZnFe2O4 hollow cubes have well-defined cube morphology with an ∼2 μm and multiple porous shell constructed from interpenetrated ZnO and ZnFe2O4 heterogeneous nanoparticles, providing structurally combined mesoporous channels for facilitating the diffusion and surface reaction of gas molecules. In addition, a comparative sensing performance investigation between ZnO/ZnFe2O4 hollow cubes and singular ZnO demonstrates that, in contrast with ZnO, the ZnO/ZnFe2O4 hollow cubes show significantly enhanced chemical sensing sensitivity towards low-concentration acetone. Furthermore, the ZnO/ZnFe2O4 hollow cubes exhibit good reproducibility and selectivity towards gaseous acetone. The enhanced sensing performance of the MOF-derived ZnO/ZnFe2O4 hollow cubes is ascribed to the unique hierarchical structure with high specific surface area, abundant exposed active sites with surface-adsorbed oxygen species and heterojunctions formed at the interfaces between ZnO and ZnFe2O4.

Amplifying the Signal of Metal Oxide Gas Sensors for Low Concentration Gas Detection

Nowadays, detection of trace concentration gases is still challenging for portable sensors, especially for the low-cost and easily operated metal–oxide–semiconductor (MOX) gas sensors. In this paper, a widely applicable amplification circuit is designed and fabricated to evidently enhance the signal of the MOX sensors by adding a field effect transistor (FET) into the conventional circuits. By optimizing the FET parameters and the loading resistance, this amplification circuit enables the commercial Figaro TGS2602 toluene sensors response effectively to the highest permissive limit (0.26 ppm) of toluene in indoor air of cars, with the detection limit of ~0.1 ppm. Furthermore, this circuit can also make the commercial Hanwei MP502 acetone sensors and MQ3 ethanol sensors response to the 1–2-ppm acetone in breath of diabetes and 2-ppm ethanol for fast and effectively drinker driver screening. The mechanism is investigated to be the gate voltage induced resistance change of the FET, with the highest theoretically estimated and experimentally measured magnification factor of 5–6. This FET amplifier can effectively enable the ppm level commercial MOX sensors response to sub-ppm level gases, promising for MOX gas sensor integration and also for other kind of resistive sensors.

Coupling p+n Field-Effect Transistor Circuits for Low Concentration Methane Gas Detection

Nowadays, the detection of low concentration combustible methane gas has attracted great concern. In this paper, a coupling p+n field effect transistor (FET) amplification circuit is designed to detect methane gas. By optimizing the load resistance (RL), the response to methane of the commercial MP-4 sensor can be magnified ~15 times using this coupling circuit. At the same time, it decreases the limit of detection (LOD) from several hundred ppm to ~10 ppm methane, with the apparent response of 7.0 ± 0.2 and voltage signal of 1.1 ± 0.1 V. This is promising for the detection of trace concentrations of methane gas to avoid an accidental explosion because its lower explosion limit (LEL) is ~5%. The mechanism of this coupling circuit is that the n-type FET firstly generates an output voltage (VOUT) amplification process caused by the gate voltage-induced resistance change of the FET. Then, the p-type FET continues to amplify the signal based on the previous VOUT amplification process.

Transilient Response to Acetone Gas Using the Interlocking p+n Field-Effect Transistor Circuit

Low concentration acetone gas detection is significantly important for diabetes diagnosis as 1.8–10 ppm of acetone exists in exhaled breath from diabetes patients. A new interlocking p+n field-effect transistor (FET) circuit has been proposed for Mn-doped ZnO nanoparticles (MZO) to detect the acetone gas at low concentration, especially close to 1.8 ppm. It is noteworthy that MZO in this interlocking amplification circuit shows a low voltage signal of <0.3 V to the acetone <2 ppm while it displays a transilient response with voltage signal >4.0 V to >2 ppm acetone. In other words, the response to acetone from 1 ppm to 2 ppm increases by ~1233%, which is competent to separate diabetic patients from healthy people. Moreover, the response to 2 ppm acetone is hardly influenced by high relative humidity of 85%. In the meanwhile, MZO in this interlocking circuit possesses a high acetone selectivity compared to formaldehyde, acetaldehyde, toluene and ethanol, suggesting a promising technology for the widespread qualitative screening of diabetes. Importantly, this interlocking circuit is also applicable to other types of metal oxide semiconductor gas sensors. The resistance jump of p- and n-FETs induced by the change of their gate voltages is deemed to make this interlocking circuit produce the transilient response.

Synthesis of Pd-loaded mesoporous SnO2 hollow spheres for highly sensitive and stable methane gas sensors

High performance methane gas sensors have become more and more essential in different fields such as coal mining, kitchens and industrial production, which necessitates the design and synthesis of highly sensitive materials. Herein, mesoporous SnO2 hollow spheres with high surface area (>90 m2 g−1) are prepared by a progressive inward crystallization routine, showing a high response of 1.31 to 250 ppm CH4 at a working temperature of 400 °C. Furthermore, loading noble metal Pd onto the surface of SnO2 hollow spheres by an adsorption–calcination process improves the response to 4.88 (250 ppm CH4) at the optimal dosage of 1 wt% Pd. Meanwhile, the working temperature decreases to 300 °C, showing the prominent spillover effect of catalytic Pd and PdO–SnO2 heterostructure sensitization as evidenced by the binding energy shift in the X-ray photoelectron spectroscopy (XPS) analysis. The response/recovery time is as short as 3/7 s and the sensitivity is stable for a test period as long as 15 weeks. All these performances show the promise of the highly porous Pd-loaded SnO2 hollow spheres for high performance methane sensors.